The key idea here is that individuals, when faced with a decision of how to vote in a direct referendum on some issue, will have good reason to believe that their individual vote will not materially affect the outcome of the vote. In such circumstances, if they vote at all they will have no reason to cast their vote for that alternative that, if adopted, would best serve their interests (or their conception of the public interest if they are of a more moral disposition), and every reason to use the opportunity to express themselves without reference to the consequences. It is as if the people operate behind a ‘veil of insignificance’—a veil that obscures all consequential reasoning. In this sense the phrase ‘the voice of the people’ picks out the idea that voting in a directly democratic setting is more like a speech act than it is like a choice between substantive alternatives, and emphasises that in contexts where talk is cheap and inconsequential it may not be entirely reliable.
Alan Hamlin, The Voice of the People, p. 371. I really like ‘the veil of insignificance’ as a way of describing expressive voting.